The present invention relates to the production of zeolite .beta. useful as an adsorbent or catalyst.
Zeolite .beta. was described for the first time in U.S. Pat. No. 3,308,069. The feature of the synthetic method disclosed here is to have present at the same time tetraethylammonium (R) ions with a silica source, an alumina source, an alkali source and water at a molar ratio of not less than 0.15 as R.sub.2 O/SiO.sub.2. However, the tetraethylammonium compound is very unstable and it is also expensive.
Japanese Unexamined Patent Publication No. Sho 61-281015 reports that the synthesis of zeolite .beta. is possible even if tetraethylammonium ions are at a R.sub.2 O/SiO.sub.2 molar ratio as low as 0.01 to 0.1. However, synthesis of zeolite .beta. in a system containing such a small quantity of tetraethylammonium ions may take 6 days for the crystallization period, even if crystallizing is done at 150.degree. C. in the presence of seed crystals.
On the other hand, M. A. Camblor et al produced zeolite .beta. in 30 hours at 135.degree. C. as reported in ZEOLITES, 1991, Vol. 11, p. 202 and p. 792, using amorphous silica, a 40% aqueous solution of tetraethylammonium hydroxide, sodium aluminate, aluminum, sodium hydroxide, potassium hydroxide, etc.
Further attempts to produce zeolite .beta. using other organic compounds in place of tetraethylammonium ions are proposed in Japanese Unexamined Patent Publications No. Sho 60-235714 and No. Sho 60-235715. These publications describe the use of special organic compounds which are rather exotic and are difficult to obtain.
The present invention provides a method in which the amount of tetraethylammonium compound required is less, common raw materials are only necessary as the raw materials, other than tetraethylammonium compound, for the synthesis of zeolite, and yet zeolite .beta. can be produced in a short period of time under mild conditions.